BOSTON – A prime-boost hepatitis C virus (HCV) vaccine regimen did not protect against chronic infection, but it did evoke immune responses and differences in viral trajectory, according to investigators in what is believed to be the first randomized, placebo-controlled efficacy trial in this setting.
There were no apparent safety concerns with the vaccine according to investigators, led by, of the University of New Mexico, Albuquerque.
“A safe and effective vaccine to prevent chronic hepatitis C virus infection is essential to reduce transmission,” Dr. Page and coauthors said in a late-breaking abstract of the study results, which will be presented at the annual meeting of the American Association for the Study of Liver Diseases.
The phase 1/2 trial described by Dr. Page and colleagues included 455 adults at risk of HCV infection because of injection drug use. They were randomized to vaccine, which consisted of a recombinant chimpanzee adenovirus-3 vectored vaccine prime plus a recombinant Modified Vaccinia virus Ankara boost, or to two doses of placebo at days 0 and 56 of the study.
There was no difference in chronic HCV infection at 6 months, the primary endpoint of the study. There were 14 chronically infected participants in the vaccine group, as well as 14 in the placebo group, for an overall incidence of infection of 13.0/100 person-years, Dr. Page and coauthors reported in the abstract.
However, there were significant differences in HCV RNA geometric mean peak at 1 month, which was 193,795 IU/L in the vaccine group and 1,078,092 IU/L in the placebo group, according to investigators. Similarly, geometric mean fold rise after infection was 0.2 in the vaccine group and 13.5 in the placebo group.
A total of 78% of vaccinated individuals had T-cell responses to at least one vaccine antigen pool, investigators said, adding that the vaccine was safe, well tolerated, and not associated with any serious adverse events.
Dr. Page had no disclosures related to the abstract.
SOURCE: Page K et al. .